Wallpapers and wall coverings are generally applied to walls using standard wallpaper pastes and adhesives based on methyl cellulose, carboxymethyl cellulose and/or starch. The subsequent removal of wallpapers presents numerous problems when new wallpapers are to be applied. To this end, the old wallpapers and wall coverings have to be removed. This is generally difficult and time consuming. The surface of the wallpaper is normally soaked with water and/or a wallpaper stripper to soften the wallpaper and the wallpaper adhesive or wallpaper paste. The wallpaper may then be removed from the wall. The task becomes particularly difficult in the case of waterproof wallpapers and wall coverings or in the case of wallpapers and wall coverings comprising a waterproof surface layer. To cope with the latter types, the waterproof layer first has to be destroyed, for example, by means of a spiked roller.
In general, the following methods are used for changing or removing wallpapers, papers and various wall coverings consisting mainly of flexible polyvinyl chloride, polyvinyl chloride foam and polystyrene:
(a) The wallpaper or wall covering is applied to a strippable lining paper. More specifically, a special-purpose adhesive or paste is first spread over the wall and the strippable lining paper subsequently applied to the adhesive or paste. Wallpapers or wall coverings are then applied to the lining paper by means of standard wallpaper pastes or wall covering adhesives. PA0 To remove the wallpaper, the lining paper is stripped so that although the wallpaper or wall covering stuck to the strippable lining paper can be removed, this can only be done once and, before the new wallpaper is hung, a new strippable lining paper has to be applied and any remains of the first strippable lining paper removed. This is of course uneconomically time consuming and expensive. PA0 (b) The dry-stripping of wallpapers can be carried out by providing the back of the wallpaper with a dehesive coating or even by impregnating the wall with a dehesive preparation. The wallpaper is then hung using a standard paste. However, the adhesive used should be suitably compatibilized with the dehesive finish. It is also known that completely dry-strippable wallpapers can be produced by providing an intermediate layer between the wallpaper and the layer of paste or adhesive by which the wallpaper is secured to the wall or substrate. British Pat. No. 1,184,563 describes a dry-strippable wallpaper consisting of a non-woven, fibrous sheet-form material which, on the side facing the wall, is coated first with a resin-like or wax-like strippable preparation and then with a layer of water-activatable adhesive. After the layer of adhesive has been activated by water, the wallpaper is secured to the wall, although it may be subsequently stripped off without having to be soaked beforehand with water and/or a wallpaper stripper. In this case, too, difficulties are involved in correctly coordinating the adhesive forces of the individual layers, quite apart from the fact that damage to the substrate can seldom be avoided during stripping. PA0 (c) Another possibility is to apply a so-called size or adhesive emulsion to the wall to be papered. For example, a size of the type in question is applied once or twice in different dilution ratios, depending on the condition of the wall, i.e. the substrate. After a drying time of several hours, normally overnight, the wallpaper can be applied to the wall thus treated using a standard special-purpose adhesive based on methyl cellulose or carboxymethyl cellulose. By contrast, papers hung using starch paste cannot be stripped, nor can heavy wall coverings hung for example with emulsion-based adhesives. In this case, too, the various adhesive forces are difficult to coordinate and the substrate, i.e. the wall, can be damaged during stripping, which means that surfacing compositions having to be applied to the wall to prepare it for repapering. PA0 (d) Special wall coverings can also be directly applied to the wall to be covered using special, suitable aqueous adhesives partly in the form of emulsions (Versois method). However, this method is attended by the disadvantage that, when the coverings are stripped off, local residues of adhesive or paste are left on the wall. In some cases, plaster may even be removed from the wall with the wall covering.
It is well known among experts that different substrates, i.e. walls of different quality, impose different demands on wall coverings in terms of hanging and, in particular, upon the adhesives used.